Si-Y-C-B-Yb as a protective matrix for SiC_f/SiC composites: Effects of infiltration temperature on microstructures and mechanical properties

To solve rapid failure of SiC Fiber-reinforced SiC Ceramic Composites (SiC_f/SiC) under water-oxygen corrosion environment, novel SiC_f/Si-Y-C-B-Yb composites was prepared in this study by Slurry Impregnation (SI) combined with Reactive Melt Infiltration (RMI) methods. Effects under different infiltration temperature on microstructures and mechanical properties of SiC_f/Si-Y-C-B-Yb composites were systematically studied. Results showed that as the melting temperature rose, no significant differences were recorded in apparent density of SiC_f/Si-Y-C-B-Yb composites while the porosity gradually increased. However, the Y diffusion layer gradually became thicker and changed from one layer to two layers due to the high temperature promoting the migration rate of Y element. Moreover, it revealed good corrosion resistance of SiC_f/Si-Y-C-B-Yb composites in 50 vol% H₂O+50 vol% O₂ water-oxygen environment. At corrosion temperatures below 1250 °C, strength retention rate of SiC_f/Si-Y-C-B-Yb composites significantly increased by 21.12 %, a value higher than that of SiC_f/SiC composites. One hand, the formation of silicate phase on SiC_f/Si-Y-C-B-Yb composites surface rose corrosion resistance, hindering further erosion from water-oxygen atmosphere. On the other hand, Oxidation activation energy of SiC_f/SiC composites was estimated to be 131 kJ/mol while that of SiC_f/Si-Y-C-B-Yb composites was 269 kJ/mol. Thus, SiC_f/Si-Y-C-B-Yb possessed excellent performance in resisting water-oxygen corrosion.